15a^2+7a-2=0,
D=169,
a1=2/3, a2=1/5,
15a^2+7a-2=15(a-2/3)(a-1/5)=(3a-2)(5a-1),
(15a^2+7a-2)/(4-9a^2)=(3a-2)(5a-1)/((2+3a)(2-3a))=-(3a-2)(5a-1)/((2+3a)(3a-2))=-(5a-1)/(2+3a)=(1-5a)/(2+3a)
15a^2+7a-2=0,
D=169,
a1=2/3, a2=1/5,
15a^2+7a-2=15(a-2/3)(a-1/5)=(3a-2)(5a-1),
(15a^2+7a-2)/(4-9a^2)=(3a-2)(5a-1)/((2+3a)(2-3a))=-(3a-2)(5a-1)/((2+3a)(3a-2))=-(5a-1)/(2+3a)=(1-5a)/(2+3a)